Linear alpha-olefin is widely used in important commercial substances such as comonomers, detergents, lubricants, plasticizers or the like, and in particular, 1-hexene and 1-octene are commonly used as comonomers for controlling density of polyethylene during preparation of linear low density polyethylene (LLDPE).
In the conventional preparation process of LLDPE (Linear Low-Density Polyethylene), copolymerization of ethylene with alpha-olefin, for example, a comonomer such as 1-hexene and 1-octene is carried out in order to control density by forming branches in the polymer backbone.
Therefore, there is a problem that the comonomer increases the production cost of LLDPE having a high content of comonomers. Many different methods have been tried to solve this problem.
Further, because the application field or market size depends on the type of alpha-olefin, a technique capable of selectively producing a particular olefin is commercially important. Recently, many studies have been conducted on a chromium catalyst for preparing 1-hexene or 1-octene with a high selectivity through selective ethylene oligomerization.
The conventional commercial method for 1-hexene or 1-octene preparation is the SHOP process of Shell Chemical, the Ziegler Process of Chevron Philips, or the like, which is used to produce alpha-olefins having a wide distribution range from C4˜C20 carbons.
Further, many studies have been conducted to selectively prepare 1-hexene or 1-octene by ethylene trimerization or tetramerization using an organic metal catalyst (J. Am. Chem. Soc 2003, 125, 5272, Ind. Eng. Chem. Res. 2008, 47, 5369, WO03/053890), but there is a still need for the catalysts exhibiting a sufficiently high activity.